1. Field of the Invention
This invention relates to a manual input keyboard for digital systems. More specifically, it refers to digital systems having a manual input keyboard that is optically activated.
2. Description of the Prior Art
In the past, typical keyboards for use in digital systems have employed contact switches for making electrical circuits. The circuit continuity identifies a particular key that has been depressed. Reed switches have been employed and in more recent time, Hall Effect sensore have been employed.
Optical keyboards have been employed in the prior art. These prior art optical keyboards involve a plurality of columns, each having an LED at one end and a photo transistor at the other, and a plurality of intersecting rows, also with an LED and photo transistor at the ends. Keys are located at the intersections of these columns and rows and when a key is depressed, both the column and row light is interrupted and the appropriate photo transistors are turned off. In this manner, a depressed key is located.
Still another prior art optical keyboard involves less than a one for one relationship between light emitters and light detectors to reduce the number of components required.
In the present invention however, blocking light is not done. Instead, a reflection of light is employed to contact a photo transistor and thereby to increase its signal output.